FIELD OF THE INVENTION
The invention pertains to gas turbines, and in particular to a gas turbine with a turbine shaft and a combustion chamber configuration that has a number of burners which in operation create an operating medium from a fuel.
Gas turbines are used in many fields for driving generators or machines. The energy content of a fuel is utilized to generate the rotary motion of a turbine shaft. To that end, the fuel is combusted in the burners discharging into the combustion chamber, air being delivered compressed by an air compressor. A high-pressure operating medium with a high temperature is created by the combustion of the fuel. The operating medium flows from the combustion chamber toward a turbine blade configuration, which typically includes a number of guide blades and a number of rotor blades. The guide blades are connected in stationary fashion to the housing of the turbine and serve to orient and smooth the flow profile of operating medium in the region in the region of the turbine blade configuration. Conversely, the rotor blades are connected to the turbine shaft, so that a transfer of the operating medium impetus to the rotor blades generates or maintains the rotary motion of the turbine shaft. The guide blades and the rotor blades are combined into sets of guide blades and rotor blades, respectively, which are connected in alternating succession one after the other in the flow direction of the operating medium.
The burners of such a gas turbine are typically arranged such that their primary axes are located on a conical surface whose axis of symmetry is the primary axis of the turbine shaft. The primary axis of a burner is then defined by its primary flame direction. It is accordingly orthogonal to its exit plane. The flow profile of the operating medium generated by these burners thus has a meridional preferential direction, so that the flow of operating medium at the combustion chamber outlet is parallel to the primary axis of the turbine shaft.
In operation of the gas turbine, to drive the turbine shaft, a sufficiently high transfer of momentum to the rotor blades is needed. However, that is unattainable by means of a primarily meridional flow of the operating medium. Therefore the first set of rotor blades, in terms of the flow direction of the operating medium, is typically preceded by a first set of guide blades. This first set of guide blades, or deflection set, is designed in such a way that the operating medium flowing in the direction of the primary axis of the turbine shaft is exposed to a tangential acceleration at the deflection set and is thus imparted a tangential velocity component. By means of this tangential velocity component, which is equivalent to a zonal component of the operating medium flow profile, the aforementioned adequate momentum transfer of the operating medium to the rotor blades is assured. However, the guide blades and rotor blades bathed by the operating medium are heated by heat exchange with this operating medium, so that in gas turbine operation, cooling of the guide blades and rotor blades is typically required. Such cooling undesirably limits the efficiency of the gas turbine.